Surgical access retractor

ABSTRACT

There is provided a patient specific access retractor for use in surgery, for example, minimally invasive spinal surgery. There are also provided methods of using the access retractor in surgery.

FIELD

The present disclosure relates generally to a surgical access retractor.More specifically, the disclosure is directed to a minimally invasivesurgical access retractor and a method of minimally invasive retractionthat expands the field of operation.

BACKGROUND

In recent years, minimally invasive surgical (MIS) approaches have beenapplied to orthopaedic surgery and more recently to spine surgery, suchas instrumented fusions involving one or more vertebral bodies.

The evolution of MIS surgery has been dependent on the development ofnew technologies. Such technologies include prosthetic devices such asscrews and rods and interbody fusion cages and access retractors, toallow the surgeon to perform placement of such devices via smallincisions and openings in the patient's body.

In regard to the lumbar spine, minimally invasive surgical technique maybe applied to the operation of transforaminal lumbar interbody fusion(TLIF). A minimally invasive transforaminal lumbar interbody fusion maybe performed by four small 2 cm incisions in the lumbar region. Theincisions are used to place pedicle screws and one of the incisions isused to place a retractor system so that the surgeon can see theanatomical elements such as the nerve roots and the intervertebral disc.The surgeon uses a retractor to perform laminectomy to decompress theassociated exiting nerve roots, perform lumbar discectomy and preparethe interbody space and then place bone graft and an interbody cage tofacilitate interbody fusion. The MIS TLIF has evolved to a stage where asurgery can be performed in a highly repeatable fashion with a highdegree of safety and reliability of outcome.

Minimally invasive surgical procedures may involve the use of a seriesof muscle dilators that separate the muscle fibers of the spine tocreate a pathway to the spine. A Kirschner wire (K-wire) is initiallyintroduced through a small incision and directed towards the spinalpathology. The position of the K-wire may be visualized by afluoroscopic imaging system to identify its location. An initial narrowdiameter muscle dilator is passed over the K-wire, and the K-wire isremoved and subsequent larger muscle dilators are continually passed.When the opening is large enough, an access tube or retractor ispositioned around the last muscle dilator through which the surgery isperformed. The inner sequential muscle dilators are then removedallowing the surgeon to operate through the tubular retractor

Furthermore a surgical device company will commonly provide a retractorset for surgery, and such a retractor set often requires multipleretractors of varying diameters and lengths as well as attachment endsto the operating table. As standard surgery requires many instrumentsand devices to perform the surgery, it incurs a substantial logisticcost. This involves:

-   -   cleaning, sterilisation and processing of all components prior        to each procedure;    -   delivery and transfer of components from the device company        warehouse to and from the hospital is time consuming and        expensive;    -   such stock must be replaced and accounted for and can be        difficult to track and validate.

Therefore, a continuing need exists for an improved device, an improvedsystem, and an improved method for performing surgery, particularlyminimally invasive spinal surgery.

The reference in this specification to any prior publication (orinformation derived from it), or to any matter which is known, is not,and should not be taken as an acknowledgement or admission or any formof suggestion that that prior publication (or information derived fromit) or known matter forms part of the common general knowledge in thefield of endeavour to which this specification relates.

SUMMARY

In one aspect there is provided a surgical access retractor formaintaining an enlarged surgical corridor, said retractor having alength sufficient to span from a skin surface through to a region ofsurgical interest, said retractor having at least a portion thereofshaped to match with the region of surgical interest, wherein the shapedportion is, at least partly, based on patient specific medical imaging.

The region of surgical interest may be a vertebral body. The region ofsurgical interest may be a pedicle.

The access retractor may be patient specific through matching the shapedportion to the morphology of the region of surgical interest. As theretractor may dock on patient anatomy in a specific way, fixation of theretractor to the anatomy may be facilitated. Fixation of the retractorto the patient anatomy may provide surgical access in an accurate,reliable and safe fashion. The specific retractor may be used as a guideto perform, for example, osteotomy and in the placement of, for example,intervertebral prosthesis and bone graft.

Advantageously, the patient specific access retractor obviates the needto have retractors of various sizes available at the time of surgery.This substantially reduces the logistics and cost of preparation ofinstruments for surgery.

The access retractor may be patient specific and procedure specific.

The shaped portion of the retractor may comprise one or more aperturesor fixation means for securing the retractor to the region of surgicalinterest.

The retractor may comprise a lip on the top face which, in use, isplaced externally on a patient's skin.

The angle of the lip may be customised based on patient specific medicalimaging.

The lip may comprise at least one aperture or fixation means forsecuring the retractor to a patient's skin.

Fixation of the retractor both at the region of surgical interest and atthe patient's skin is advantageous as it obviates the need forextraneous attachment, such as via an arm to a surgical table.

As the retractor is patient specific, various features may be includedin the retractor design which are also patient specific. The placementof features in the retractor may be enabled through patient imaging andcomputer aided design. The features may be, at least partly, located inthe shaped portion of the access retractor.

Specific grooves or channels may be incorporated into the retractor toconform with the contour of the retractor and/or conform with patientspecific anatomy, in such a way as to mark, localise or performpredetermined surgical intervention. In this way, the access retractormay be used to guide instruments; for example to perform osteotomy,monitor neural function, guide instruments to perform intervertebraldisc clearance and preparation or to guide, place and deliver anintervertebral cage prosthesis in an accurate manner.

The shaped portion may comprise one or more guides for cutting bone. Theguides may be positioned in the retractor based on preoperative medicalimaging.

These features are selected and predesigned into the retractor so thatthe surgeon may accurately perform procedures.

The retractor may be designed by using a combination of computer aideddesign software and patient morphological data obtained by medicalimaging. For example, vectors may be determined to run along the centreof pedicles of the spine. In this way the intersection of the vectorwith the surface of the patient's skin may be precisely determined.Further, the length of the vector from the surface of the skin to theintersection with a particular region of surgical interest, such as abone interface, may be determined.

Through the characterisation of the vector, computer design software maybe used to create patient specific dilators to allow progressivedilation of a patient's tissue to a predetermined depth andcircumference around the vector replicated by, for example, a wire, suchthat the patient specific access retractor can be implanted into thepatient.

The patient specific access retractor may incorporate a predesignatedvector so that it may be guided by way of a K-wire to allow preciseplacement of the access retractor onto the anatomy to be localized, suchas the spine. The point of contact of the retractor with both the skinsurface, and the anatomy to be localised at the base of the retractormay be contoured in a patient specific manner using computer aideddesign software.

Once the patient specific shape of the retractor is determined, theretractor may be manufactured using three-dimensional printing.

One or more fixation points corresponding to the intersection of thevector with the selected anatomy may be incorporated into the retractor.The fixation may be by way of a cannulated screw which is guided down aK-wire and inserted into the patient's bone in such a way that theretractor is then secured to the bone. It will be appreciated that acannulated screw is one method of securing the retractor. Other methodsmay include staples or pins.

The patient specific retractor may also incorporate ancillary channelsto allow suction of fluid from the internal aperture of the device orirrigation of fluid into the internal aperture of the device.

Dilators may be used to assist in placement of the access retractor andmay incorporate components that allow electrocautery by way of diathermyto be used at the tip of the dilator where the interface of tissue andbone occurs. Such dilators may also include components that allowneurophysiological monitoring of the surrounding tissue and associatedstructures. The dilators may also contain channels to allow irrigationand suction to occur.

The patient specific retractor may also incorporate components to allowdiathermy and cauterisation of surrounding tissue.

The patient specific retractor may be impregnated with antimicrobialsubstances or surface coatings to reduce the risk of infection.

The patient specific retractor may incorporate radio-opaque markers toallow verification of positioning by way of image intensification.Preferably this would not be to the extent that they would obscurepatient anatomy.

The patient specific retractor may facilitate localisation to otherareas of anatomy, for example to harvest bone graft without instrumentsor for reconstructing donor site anatomy.

The access retractor may also incorporate components to allowelectrophysiological monitoring of surrounding structures and tissue.

Furthermore a guide or groove within the retractor may be used tofacilitate suction or aspiration of fluid and gas from the working area.

Furthermore an access aperture or groove may be used to facilitateirrigation of fluid into the working area.

Electrophysiological sensors may be placed beside the access retractorin pre-set locations to facilitate neural monitoring in the workingarea.

The retractor may comprise any combination of the hereinbefore disclosedembodiments.

In another aspect there is provided a method for designing a patientspecific access retractor comprising the steps of:

-   -   -   a) determining one or more trajectories from a region of            surgical interest to the skin surface of a patient using            preoperative medical imaging;        -   b) determining the morphology of the region of surgical            interest using preoperative medical imaging; and        -   c) designing an access retractor, said retractor having a            length sufficient to span from a skin surface through to the            region of surgical interest, said retractor having at least            one portion shaped to dock with the region of surgical            interest, wherein the shape of said portion is based, at            least in part, on patient specific medical imaging.

In another aspect there is provided a method for manufacturing a patientspecific access retractor comprising the steps of:

-   -   -   a) determining one or more trajectories from a region of            surgical interest to the skin surface of a patient using            preoperative medical imaging;        -   b) determining the morphology of the region of surgical            interest using preoperative medical imaging;        -   c) designing an access retractor, said retractor having a            length sufficient to span from a skin surface through to the            region of surgical interest, said retractor having at least            one portion shaped to dock with the region of surgical            interest, wherein the shape of said portion is based, at            least in part, on patient specific medical imaging; and        -   d) manufacturing the access retractor.

In any of the hereinbefore disclosed embodiments the region of surgicalinterest may be an anatomical body.

In any of the hereinbefore disclosed embodiments the anatomical body maybe a vertebral body. The vertebral body may be a pedicle.

In any of the hereinbefore disclose embodiments the medical imaging maybe computed tomography.

In any of the hereinbefore disclosed embodiments the access retractormay be manufactured using rapid prototype technology.

In any of the hereinbefore disclosed embodiments the access retractormay be manufactured using three-dimensional printing.

In any of the hereinbefore disclosed embodiments the trajectories may berepresented as three-dimensional images with the aid of suitablecomputer software. The trajectories may be determined to meet the skinat particular entry points.

The access retractor may be manufactured from a suitable compatiblepolymer, such as, for example, polyether ether ketone.

In another aspect there is provided a use of an access retractor ashereinbefore disclosed in a surgical procedure. The surgical proceduremay be spinal surgery. The surgical procedure may be minimally invasivespinal surgery. The surgical procedure may be spinal fusion. Thesurgical procedure may be transforaminal lumbar interbody fusion (TLIF).

In another aspect there is provided a method for accessing a region ofsurgical interested comprising the steps of:

-   -   -   a) providing a retractor according to any one of the            hereinbefore disclosed embodiments;        -   b) docking at least part of the shaped portion of the            retractor via a surgical corridor to the region of surgical            interest; and        -   c) fixing said retractor to the region of surgical interest.

The retractor may also be fixed to the skin of the patient via asuitable fixation method. For example via an aperture in the lip of theretractor.

Throughout this specification, use of the terms “comprises” or“comprising” or grammatical variations thereon shall be taken to specifythe presence of stated features, integers, steps or components but doesnot preclude the presence or addition of one or more other features,integers, steps, components or groups thereof not specificallymentioned.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a plan view of an access retractor according to anembodiment of the present disclosure.

FIG. 1(b) is a plan view of an access retractor according to anembodiment of the present disclosure.

FIG. 1(c) shows a cutaway of an access retractor according to anembodiment of the present disclosure.

FIG. 1(d) is a side elevation of an access retractor according to anembodiment of the present disclosure.

FIG. 1(e) shows a section through plane A-A of the access retractor ofFIG. 1(a) according to an embodiment of the present disclosure.

FIG. 1(e) shows a side elevation of an access retractor according to anembodiment of the present disclosure.

FIGS. 2 to 5 show a computer designed access retractor in use accordingto an embodiment of the present disclosure.

FIG. 6 is an enlargement of FIG. 1(c).

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Before the present devices and/or methods are disclosed and described,it is to be understood that unless otherwise indicated this disclosureis not limited to specific devices, components, designs, methods, or thelike, as such may vary, unless otherwise specified. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting.

It must also be noted that, as used in the specification and theappended claims, the singular forms ‘a’, ‘an’ and ‘the’ include pluralreferents unless otherwise specified. Thus, for example, reference to ‘aguide wire’ may include more than one guide wires, and the like.

Disclosed herein are advantageous devices and methods for performingsurgery, particularly spinal fusion surgery.

In an exemplary embodiment a patient specific access retractor isprovided. Once the depth of tissue to be accessed by the retractor isknown from patient medical imaging, standard design may be applied tothe external or top part of the retractor. This may extend toapproximately 80% of the depth of the access retractor. The finalapproximately 20% may be designed in a specific way to contour match themorphology of the patient's anatomy and in particular, the region ofsurgical interest.

A guidance aperture may be within the retractor where a Nitinol K-wireis used to localise the retractor to the patient specific anatomy. Theguidance aperture may also allow placement of a cannulated screw tosecure the retractor to the patient's spine. Within the guidanceaperture may be specially designed grooves, which facilitate placementof instruments in locations within the working area of the accessretractor. Such grooves may be used to place mark-to-mark osteotomylines on the patient's bone and then guide instruments into theinterbody space. The access retractor may also comprise an attachmentfor a Nitinol K-wire on the rosteral side of the intervertebral disc tobe operated on. This facilitates attachment of the access retractor tothe patient. The access retractor may have apertures or instrumentguides such that a fibre optic light source may be attached. The accessretractor may have a guide or facility for the use of diathermy at thebase of the retractor. The customised portion of the retractor may havediathermy points or a guide for the use of such points in the equipmentsuch that the tissue can be cauterised.

In order to evolve the manufacturing procedure to a greater level ofergonomic efficiency, safety and best possible patient outcomes,three-dimensional printing technology has been used to facilitate theseoutcomes.

Three-dimensional printing is a process whereby layer basedpolymerisation of a resin or powder is used to produce a solid object.This technology has been applied to producing solid replicas of anatomywhich has been captured by medical imaging.

Three-dimensional printing technology has been used extensively incomputerised design product development prototyping and more recentlydirect manufacturing of objects. It has been possible to integratecomputer design and anatomical biomodeling information to providecustomised prosthetic implants for the human body. This disclosure usesrapid prototyping technology to facilitate interbody fusion by way ofthe minimally invasive transforaminal interbody fusion technique.Three-dimensional bench top printing has been integrated with diagnosticsurgical planning, surgical navigation and by way of patient specificminimally invasive access retractors.

The patient specific access retractor may also be used for harvestingbone graft. A second retractor may be manufactured by three-dimensionalprinting to dock on the iliac crest or other part of the skeleton toharvest bone graft. In this embodiment, a vector is created from eitherthe right or left iliac crest which crosses the skin at the same point,if possible, as one of the vectors identifying the pedicle of theselected vertebra. Alternatively, a vector exiting at a separate pointwould be another option. The depth of tissue from the surface to theiliac crest or bone donor site is determined. The retractor is againcontour matched to the surface of the iliac crest or bone donor site andthe length and diameter of the retractor is then constructed inthree-dimensional design software. The retractor incorporates a guidefor placement along a K-wire that has been fixed to the iliac crest bonedonor site. The retractor is then manufactured by way ofthree-dimensional printing in a bio-compatible material. At the time ofsurgery, the surgeon places a Jamshidi needle into the iliac crest orsuitable bone donor site and places a K-wire. The K-wire is then used toguide the retractor to the iliac crest or bone donor site and acannulated screw is then used to secure the retractor to the crest. Theretractor may act to guide instruments to harvest bone graft by way ofspecific channels and grooves within the retractor.

Referring to FIG. 1(a), access retractor (1) is illustrated. Theretractor has a fixation point (2), located on the shaped portion of theretractor, for fixing to an anatomical body and guides (3) tofacilitate, for example, the introduction of instruments. An aperture(4) on the retractor lip is available to secure the retractor to thepatient's skin.

Referring to FIG. 1(b), a guide (3) for instrument introduction ishighlighted.

Referring to FIGS. 1(c) and 6, the portion (5) of retractor (1) isshaped based on patient specific information so as to dock with a regionof surgical interest.

Referring to FIG. 1(d), lip (6) is angled based on patient specificmedical imaging.

FIG. 1(e) depicts a section A-A through retractor (1) of FIG. 1(a). Thesection shows fixation point (2) and other shaped structure (7).

FIG. 1(f) indicates the length of the retractor to be 60 mm, that is,the length from the region of surgical interest to the surface of theskin.

FIGS. 2 to 5 illustrate various computer simulations of retractor (1)fixed in place on vertebral body (8). FIG. 3 shows a cutaway of thetissue surrounding the vertebral body with retractor (1) fixed in place.FIG. 4 is similar to FIG. 3 but the tissue (9) is now illustrated withthe lip (6) of the retractor is located external to the tissuestructure. FIG. 5 shows retractor (1) fixed in place on a vertebral body(8) with the shaped portion (5) docking with the vertebral body.

While the foregoing description has focused on spinal surgery, it iscontemplated that the retractors and methods described herein may finduse in a wide range of surgical applications. Thus, where it is desiredto insert a screw or pin into bone in a minimally invasive manner, orotherwise to access a surgical target site via an instrument, theretractors and dilators of the present disclosure may be used.

It is to be understood that while the present disclosure has beendescribed in conjunction with the specific embodiments thereof, theforegoing description is intended to illustrate and not limit the scopeof the disclosure. Other aspects, advantages and modifications will beapparent to those skilled in the art to which the disclosure pertains.Therefore, the above examples are put forth so as to provide thoseskilled in the art with a complete disclosure and description of how tomake and use the disclosed devices, and are not intended to limit thescope of the disclosure.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited.

All documents cited are herein fully incorporated by reference for alljurisdictions in which such incorporation is permitted and to the extentsuch disclosure is consistent with the description of the presentdisclosure.

1. A surgical access retractor for maintaining an enlarged surgicalcorridor, said retractor having a length sufficient to span from a skinsurface through to a region of surgical interest, said retractor havingat least one portion shaped to match with the region of surgicalinterest, wherein the shape of said portion is, at least in part, basedon patient specific medical imaging.
 2. A surgical access retractoraccording to claim 1, wherein the length sufficient to span from a skinsurface through to a region of surgical interest is determined bypatient specific medical imaging.
 3. A surgical access retractoraccording to claim 1, wherein the region of surgical interest is ananatomical body, such as a vertebral body.
 4. A surgical accessretractor according to claim 1, wherein the region of surgical interestis a pedicle.
 5. A surgical access retractor according to claim 1,wherein the shaped portion of the retractor comprises one or morefixation means for securing the retractor to the region of surgicalinterest.
 6. A surgical access retractor according to claim 1, whereinthe retractor comprises a lip on the top face which, in use, is placedon patient's skin.
 7. A surgical access retractor according to claim 1,wherein the retractor comprises at least one fixation means for securingthe retractor to a patient's skin.
 8. A surgical access retractoraccording to claim 6, wherein the angle of the lip is customised basedon patient medical imaging.
 9. (canceled)
 10. (canceled)
 11. (canceled)12. A surgical access retractor according to claim 1, wherein theretractor comprises antimicrobial substances or surface coatings toreduce the risk of infection.
 13. A surgical access retractor accordingto claim 1, wherein the retractor comprises radio-opaque markers toallow verification of positioning by way of image intensification. 14.(canceled)
 15. A surgical access retractor according to claim 1,wherein, in use, electrophysiological sensors are placed beside theaccess retractor in preset locations to facilitate neural monitoring inthe working area.
 16. A surgical access retractor according to claim 1,wherein the retractor comprises ancillary channels to allow suction offluid from an internal aperture of the device or irrigation of fluidinto an internal aperture of the device.
 17. A method for designing apatient specific access retractor comprising the steps of: a)determining one or more trajectories from a region of surgical interestto the skin surface of a patient using preoperative medical imaging; b)determining the morphology of the region of surgical interest usingpreoperative medical imaging; and c) designing the access retractor,said retractor having a length sufficient to span from a skin surfacethrough to the region of surgical interest, said retractor having atleast one portion shaped to dock with the region of surgical interest,wherein the shape of said portion is based, at least in part, on patientspecific medical imaging.
 18. A method for manufacturing a patientspecific access retractor comprising the steps of: a) determining one ormore trajectories from a region of surgical interest to the skin surfaceof a patient using preoperative medical imaging; b) determining themorphology of the region of surgical interest using preoperative medicalimaging; c) designing the access retractor, said retractor having alength sufficient to span from a skin surface through to the region ofsurgical interest, said retractor having at least one portion shaped todock with the region of surgical interest, wherein the shape of saidportion is based, at least in part, on patient specific medical imaging;and d) manufacturing the access retractor.
 19. A method according toclaim 17, wherein the region of surgical interest is an anatomical body,such as a vertebral body.
 20. A method according to claim 19, whereinthe vertebral body is a pedicle. 21-30. (canceled)
 31. A method foraccessing a region of surgical interested comprising the steps of: a)providing a retractor according to claim 1; b) docking the shapedportion of the retractor via a surgical corridor to the region ofsurgical interest; and c) fixing said retractor to the region ofsurgical interest.
 32. A method according to claim 31, wherein prior todocking the shaped portion of the retractor to the region of surgicalinterest one or more dilators are utilized to increase the width of thesurgical corridor.